In Spanish, there are two types of verbs that undergo spelling changes during conjugation. The first, spelling change verbs, undergo consonant changes in certain conjugations. The second, stem-changing verbs, are characterized by changes in vowels.

 

Stem-changing verbs have a vowel spelling change in the stem of all forms except nosotros and vosotros. The endings themselves are the same as for regular –AR, -ER, and –IR verbs. Spanish has three stem-changing patterns in the present tense: E to IE, O to UE, and E to I.

 

E changes to IE

 

Example: cerrar – to close

 

Pronoun	Regular –AR Ending	Conjugation /w E:IE Stem-Change
yo – I	o	cierro
tú – you (familiar)	as	cierras
él, ella – he, she usted – you (formal)	a	cierra
nosotros, nosotras – we	amos	cerramos*
vosotros, vosotras – you (plural familiar)	áis	cerráis*
ellos, ellas – they ustedes – you (plural formal)	an	cierran

 

* Note the lack of a stem-change in the nosotros and vosotros forms.

 

O changes to UE

 

Example: PODER – can, to be able to

 

Pronoun	Regular –ER Ending	Conjugation /w O:UE Stem-Change
yo – I	o	puedo
tú – you (familiar)	es	puedes
él, ella – he, she usted – you (formal)	e	puede
nosotros, nosotras – we	emos	podemos
vosotros, vosotras – you (plural familiar)	éis	podéis
ellos, ellas – they ustedes – you (plural formal)	en	pueden

 

E Changes to I

 

Example: REPETIR – to repeat

 

Pronoun	Regular –IR Ending	Conjugation /w E:IE Stem-Change
yo – I	o	repito
tú – you (familiar)	es	repites
él, ella – he, she usted – you (formal)	e	repite
nosotros, nosotras – we	imos	repetimos
vosotros, vosotras – you (plural familiar)	ís	repetís
ellos, ellas – they ustedes – you (plural formal)	en	repiten